The subject matter disclosed herein relates generally to diagnostic imaging systems, and more particularly to nuclear medicine (NM) imaging systems such as positron emission tomography (PET) imaging systems and scatter recovery for detectors of the imaging systems.
PET imaging systems typically generate images depicting the distribution of positron-emitting nuclides in patients. The positron interacts with an electron in the body of the patient by annihilation, with the electron-positron pair converted into two photons. The photons are emitted in opposite directions along a line of response. The annihilation photons are detected by detectors (that are typically in a detector ring assembly) on both sides of the line of response on the detector ring assembly. These detections are termed coincidence events. The coincidence events detected by the PET detector ring assembly are typically stored within data structures called emission sinograms, which is a histogram of the detected coincidence events. An image of the activity distribution within a patient's body is generated from the emission sinograms through a process called image reconstruction.
In PET imaging systems having multiple detector units (detector units with dedicated event detection circuitry), the incident gamma ray can interact in the scintillator of a detector unit resulting in a lower energy scattered gamma ray. If the scattered gamma ray leaves the scintillator block of the detector unit, the gamma ray will produce an event with an energy equal to the difference between the incident gamma ray's energy and the energy of the scattered gamma ray. If the scattered gamma ray interacts in the scintillator of a neighboring detector unit, the gamma ray may produce a second event with an energy equal to the scatter gamma ray's energy. The partial energy events are often discarded by conventional PET imaging systems as potentially representing scatter from a source other than the detector (e.g., patient scatter or object in the detector field of view). Gamma rays that scatter before reaching the detector unit should be rejected since the gamma rays will provide misinformation with respect to the line of response of the gamma rays. Accordingly, the sensitivity of the PET system is decreased.